Conversation-registering circuits for machine-switching telephone systems.



. Y l y 'FL'ALDENDQRFFI c :oN'vERsAIIoNmamsemNG mculs 'Foav MACHINE SWITCHING -TELEPHONE SYSTEMS.

Patented July 27,

5 SHEETS--SHEET I.

APPucATloN 'mtu JUN; 3o. 1913.

'n ALDENDORFF.y l l CGNVERS'TI-O'N,RE`G`ISTE`R'ING CIRCUITS FOR MACHINE S'WITCHING TELEPHONE SYSTEMS.

Km 1 Qu .12 (,n E y H mn e .JMh V ds 65 H .m Lw. a ,D1 mw w. w m, H. U m NM.. .7..v .cv m a l F. ALDI-:Nanna CONVERSATION REGISTERING CIRCUITS FOR MACHINE SWITCHING TELEPHONE SYSTEMS.

APPLICATION FILED )UNE 30, 1913. 1,147,997. Patented July 27, 191.F

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.K 04 im W m F. ALDENDORFF. CONVERSATION REGISTERING CIRCUITS FOR MACHINE SWITCIIING TELEPHONE SYSTEMS.

APPLICATION FILED IUNE 30, I9I3. v A 1,147,997. Pand'July 1915.

5 SHEETS-SMH 4.

Fig. 4.

F'. 4ALDINDOFIFF. CONVERSATION REGISTERING CIRCUITS FOR MACHINE SWITCHING TELEPHONE SYSTEMS'.

APPLICATION FILED JUNE 30, 1913.

Patented Julyl 27;

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UNITED STATES 'PATENTA OFFICE.

FRITZ ALDENDORFF, OF MORTSEL, N EAR ANTWEBP, BELGIUM, ASSIGNOB TO WESTERN' ELECTRIC COMPANY, or NEW YORK,

N. Y., A CORPORATION OF ILLINOIS.

CONVERSATION-REGISTERING CIRCITS FOR MACHINE-SWITCHING TELEPHONE' SYSTEMS.

Specification of Letters Patent. Patented J i115'T 27, 1915.

Application filed .1f une 30, 1913. 1 Serial N o. 776,614.

To allie/10m. it may concern:

Be it known that I, FRITZ' ALDENDORFF, 'a suhjectof the King of Great Britain, residing at Mortsel, near Antwerp, in the Province of Antwerp and Kingdom of Belgium, have inventedA a vcertain new and useltele )hone systems in which the connections ma e between different stations are registered and'charged to the stations-that 1nitiate the-calls. 1

" vA feature of the invention consists inthe manner in which the recording circuit is` closed through 'a wire that serves aspart'ofa circuit for other purposes such as restoring the switchesy used for a connection to their normal "positions, preparing a circuit that momentarily removes the busy'condition from a calling line in the case of a re- 'vertive callin .a party line system and for disconnecting devices from a calling line after they have `[.e1forme'd vtheir functions so as to prevent them from absorbing any of the` talkingcurrent.v According to the invention all these functions are accomplished over a single wire. by straight battery currents, that is without employing graded or differential currents. Synchronousv circuit changers are used which apply portions of the various circuits to different points of the wire at identical moments.

Another feature of the invention is vthe provision of a special conversationmeter for eachA station of a party line and of means i for connecting the-meter corresponding to 'the calling station to the meter circuit. The

meter selectingdevices are also -made to act as a' means for 'startmga switch or-swltches 'that connecte lcalling line toan idle'link circuit through which the circuit'jof the lcalling' line is extended to the 'wantedline A further feature ofthe invention resides party. This is important in cases of revertive calls. If.- in such cases the meter circuits at the exchange were to be 'closed' .in the well-known manner, by. the Amere closure of the circuit of the called line on the response of the called subscriber it is evident that the meter circuits would be caused to act inl the case of revertive calls, even if the called station did -not answer because at the moment the revertive connection is made the circuit of the party line is alreadyclosed at the calling station. Hence means must be provided for closin-gftlie meter circuit that do not respond to the ordinary closure of the loop of theavanted' line. The means provided byrtliis'invention consist of contacts attached` to the switchhooks of the subscribers station that momentarily establish alspe'cial condition of the line that differs fromthe normal and from the closed speaking-condition, and these means consist further of devices that respond only to the aforementioned special condition.

4Another feature of the invention consists in providing improved devices for removing -the busy vcondition from a calling part)1 line at the moment a revertive connection is made.

The improvement consists in sc 'arranging these devices that this busy potential is -removed only atv the instant the revertive connection ismade, and not as in systems heretofore proposed, also incidentally at other instants. 1

Further features of the invention will appea'r in the following specification.

"Ti're invention is shown-in the accompanyingi" drawings.

Figure 1 illustrates the `'circuits of a dis-1 "tributmg switch, which connect'.` acalling line to a free trunk leading toa selector. In this figurey the circuits of the conversation meters'belonging to a party line are also illustrated.` lFig. 2 represents the-circuit of a first selector. Fig. 3 shows the circuits of a final selector. Figs..4, 5, 6 and 7 show the partyl line subscriber equipments.

Fig.l 8 illustrates `the impulse tansmitter partly in perspective and partly diagrammatically. Fig9 is a diagrammatic representation of` the impulsel transmitter, kand Fig. 10 shows special relay designed for a positive release. p 201.ancl 2072 "represen't the two limbs of a line connected` to the evchange.- It will be .assumed that four subscribers equipments as illustrated in Figs. 4, 5, 6 and 7 1 are conhook. Upon the removal of the receiver,v

the upward movementcf the switch hook 205, thence through 7, 8, 9, 10, 11,. meter connecting relay 213 to the negative pole of 13, armature contact 12 of restoring relay 217, tothe positive pole of the battery. They 'meter 206 which corresponds to the calling 1Y0 pushes the springA 600 into Contact `with meter connecting relay 213 to themeter cirspring 601. In the case of the station shownA in Fig. 4', this upward movement 'of the- 1 switchhook momentarilygrounds the line 201' 'through aresistance 6 05. f Inl the sta.- V'tion illustrated in Fig. 5, lthe line limb 202` is momentarily grounded, and in the stai tion shown in Fig. 7 4line limb 201 is momentarily grounded througha resistance v606 and the limb 202 is simultaneously-mo-4 2o-mentari1y directly grounded.- The upward mov/ ement of the switch hookv 603 ,inthe subscribers equipment shown' in. Figf, causes a momentary Contact between springs 600 andv 601, which momentarily short -2'5 circuits the line Without any interyening re- ,sistance, or, in other words, thevloop vconsisting of the line leads 201 and 202 is `short circuited before the switch hook `closes the loop through contact 607 and hence through J0 the transmitter 608 and the winding 609 of vthe induction coil. This momentary grounding of the one or the other or both of the line limbs 201 and 202 in the manner illustrated is the means by which thepr'oper ..55 meter is connected to the meter circuitY of A The momentary short. cir-V the exchange.

,ctriting'of the lineloop in the manner shown lnFig. 6 does not perform any useful function when this subscriber is' calling.` This `40 momentary short circuiting iswuseful only when'this subscriber isthe called party. In this case the momentary short circuitin o 'f the line loop causes the relay 610 at the nal selector to attract its armature momentarily and thus to energize relay 519 which in turn moves the side switch at the final selector from the ringin to the talking position as will be more ful y explained hereinafter.

By the fourv different switchingjmeasures described, the relays 203, 202, 205 at the exchange are influenced in 4dierent ways, so.

that these relays connect either the meter 206, 207,208 or 209 to the meter circuit 210.

tracedtrom earth through battery 211,

winding of relay 205, winding of relay 203, ,60 wire 3, armature 4 of line extending relay 212, Wire 201, switchhook vof station I to earth. Bythe actuation of relays 203, 205,

l a currentv is caused totlow through the meter connecting relay 213. This-current may ,b e

' '.traced' 'from-'the positive vpole of the ex.

station No. I of line 201, 202 is now connected through the'armature contact '15.of' a' cuit 210.

' change battery through armature 6 of relay If a station II of li ne.201,v202`.hadcalled,` this would have caused'the energization vof relays 204, 205 instead of relays 203 and 205,

'and this'would have resulted in they energization ofthe meter connecting relay 2141 by al current flowing over the following path :-Positive pole'o the battery, contact 6, wires 7, 16, Contact 17 of rela-y 204, wire 18, contact 19 of relay 203, wire v20, meter connecting relav 2li 'to the nega-tive pole of the battery.

The. meter connecting relay 214 would have closed a locking circuit for itself through 22, 21, 13, '12, tio the positive pole of the battery, and the meter 207 corresponding to the calling station II Jwould 'only when station IIIv calls.

- be `connected to the meter circuit 210 through the armature 23 of a meter-connecting relay 214.

If it had been a station III that called,

the switchhook of this station would have earthed wires 201, 202, the one wir'ebeing earthed .direct, the other through a resistance so that the windings 1 and 2 ofthe differential' relay 205 would have been ener` gized by currents of different strengths," causing. this relay to attractits armatures, this relay being so wound as to be-unaifected when currents of equal strengths flow,-

through windings -1 and 2. Thus the three relays 203, 204 and 205 all pull up together in the energia/.ation of the meter connecting relay 215v by aA current flowingfrom the 9, 2l, 23, 26,m'eter connecting re a "2 15vto the negative pole'of the battery. T e meter.

This results .111,0 `positive pole of the battery throu h', 7, 8,.

connecting relays 213, 2111 are prevented from beingvenervized by the o nl -of armature contact 10 and, 19.: mg

13, and armature Contact 12. e,V -met connectlng relay 215 connects meter 208 that ture contact 29 to the meter circuit`210. y In case station IV calls, the switchhook manneny 'Ihis results in only' thev relaysl .203, 204 being energized, the differential i connecting relay 215 closes a locking for itself through it'sarmature 27- iaoj corresponds to station III through its armarelay 205 remaininginert. .-Byj the relays 203, 204 being energized alone,'-the meter '.connectin'grelay 2164 is actuated by current iso 'flowing' from the 4positive pole of the bat- -tery througharmature 30, Wire31, arma- "nectingv relay 216 throug'fh the energization of the relays 203 and 2041. The relays 203, 204:-are, however, energized lby thel calling of anyf'cfthe stations I, II, III, IV' as soon as the switchhook of any of these stations .closes -the 4line loop. For this reason the circuit of the -meter -connecting relay 216 must beopen in all cases in which the relays S- and 204 shall not effect the connection of the meter209 to the meter circuit 210, so

this opening of the circuit of the meter con- -nectingrelay must take place before the closure of the line loop 201, 202.- This opening of the meter connect-ing relay circuit is caused by the relay 21S. This relay is energized the moment any one of the meter con;

' necting relays 213', 214, 215 is actuated' and the circuit through the relay 218 is closed either by armature 39,V 39 or 39 according as the meter connecting relay 213, 211 or 215 is energized. The closure of either of the contacts 39, 39', 39 takes place a moment before the subscribers loop 201, 202 is closed,

so'that by the time the relays 203, 201 are energized by the closure of the loop. the armature 35 o' relay 218 will already have opened the circuit of the meter connecting relay 216fat the armature The relays 203 and 204, besides serving to close the circuit of the meter connecting relay 216, are also used for closing the circuit of a relay 219, which relay controls the cir- 'cuit of the stepping or power magnet 220 .of the distributing switch. This distribut- :1n

switch'ha.ving movable contact arms 2,50, 251 and 252 .that are driven step 'by step in a known manner by the magnet 220,

i so as to wipe over sets of fixed contacts connected to trunks 253, 254, 255 leading to first selectors, Fig. 2. The moment the line loop 201, 202 is closed, and the relays 203, 204 energized, a circuit is closed from the vpositive, pole vof the battery through they ture contact 47, stepping magnet 220, positive pole of the battery. The stepping magnet 220 now causes the arms 250,. 251 and 252 to travel step by step over sets of fixed contacts connected to the trunks leading to the first selector, Fig. 2. The moment the contact arms 250, 251, 252 leave their normal position the contacts 15, 46 andA 51 of an off-normal switch belonging to -the dis'- tributing switch are opened, and the contacts 49, 50, 52, 53, 55 and 56 of this offnormal switch are closed. For convenience of illustratlon, the contacts of thls' offy normal switch are shown in different parts of the drawing, although in practice they will all form part of one and the same switch. A

.By the closure of' contact 52, the test wire 256 extending from the calling line tothe vContact banks of the final selectors of the exchange is earthed, and the busy condition of the calling line is thus indicated.

"llhe` test circuits of theA distributingv `switch, Fig. 1, are so arranged that the test relay 2,19 remains energized as long as the test biglsh 252 keeps striking earthed test contacts 257, Fig. 2. As long as this continues the circuit 'of the test relay 219 will remain closed, current flowing through the test relay over a circuit leading from the negative pole of the Abattery to armature contact 31, contact 55 of off-normal switch, which is now closed. test relay 219, test wire 57, test brush 252, fixed contacts 257 of the busy trunks, thence through the test wires 58 to the test brushes 252 of other. distributing switches that are keeping the trunks busy that are being trayersed by the hunting switch, wires 57 of the other distributing switches, contacts 5G of the switches, armatlu'e'contactsf59, and wires 60 of same, movable contact arms 61 of synchronous circuit changers belonging to the other distributing switches, coils 62 and thence to earth.- The moment the test brush 252 of the distributing switch that is .hunting for an idle trunk reaches the fixedcontact 257 belonging to an idle trunk, the circuit traced above for the vtest relay 219 willv no longer be closed, and the test relay 219 will allow its armatures to drop back. The armature contact 3.4 of the test relay will open -before contact 59 is closed, so that the circuit of the test relay vcannot be reclosed ilnmediately after through the circuit leading from' the negative pole of the battery through 31, 63, 55, 219, 56, 59, 60, 61, 62 to earth. The moment the contact- 59 is closed, thc test` wire of the trunk that was found idle is earthed ove/r a path leading from the fixed contact 257 through 57, 56, 59, 60, A61, 62 to earth. The denergization of. the test relay 219 causes the closure of the line-extending orfcut-ofl' relay 212, through a circuit from earth through 61 and through a t ,thefirst selector,

contact i9 of the off-normal switch 65, 212 to the negative pole of the battery. By the energization of the relay 212 lthe wires 201, 202 are separatedfrom the relays 203 and 204, andare extended to the movable contact arms 250 and 251 of the distributing switch, and throu h these movable arms to l ig.v 2. I When the 'line is thus extended to the first selector the relays 224 and 225 areenergized.. In order to ets- 4tablish the desired connection through the automatic switches at vlthe central. oiiice, the

calling subscriber now sends impulses to the exchange by Working his impulse transmitter. v 1 l The impulse transmitter is shown in Figs.

. 8 and 9. 700'represents a disk that may be turned about a shaft 701 by the well known type 'of finger wheel. The finger wheel for turning the disk 700 forward and the spring forfreturning the same to its normal 'posi- 'tion' when the-*finger wheel is released, are f l omitted as arevalso all other parts in connectin with the vimpulse transmitter which 25. y -The disk 700 .is divided into two parts, 702

are not essential to make'it comprehensive.

and 703, These' parts are insulated from one another. .The part 702 of the disk 7 00 consists of an electric conductor on the surface l of which a brush 7 04 makes contact, which in tlie normal position of the disk 700 bears upon an yinsulating portion 705. .The purose ofthe disk702 is to ground the brush 04 whenever the disk,700 is moved out of its normal position. The ground connection to the disk702 is indica-ted at 706. The

part 703 ofthe disk 700 is insulated and is equipped with a. number of pins 707', 7072, 7 073', 707* and 708 extending outwardly from its surface. 709 when the disk is turned out of its normal position. Thepin 708 in the same manner engages with the Contact spring 710.

lVhen the disk 700 is turned forward as indicated by the arrow, the springs 7 09 and v710, rwhich are normally in contact with spring |211 and 712 respect1vely,-are merely moved farther in thev direction of contact.

Thusiih'en a calling subscriber removes his receiver from the hook 603, which in turn closes the linecircuit at contact 007 and then turns vthe disk 700 in the direction indicated by the. arrow, the brush 704 will ground to two line limbs 201 and 202 through the rroundingdisk 702. Immediately after the brush 704 commences ridingupcn the con ducting portion 702, the pm 708 sweepspast the spring 710. Directly afterthis the pins 707 commence sweeping past the spring -709. After the subscriber turns the linger wheel from the third-hole to the stop (not shown) and then releases the finger wheel,l

the disk 700 "will return to its normal position and in this movement it will first openv the ground connection through line lim'b 201 The pin 70.7 engagesa spring three times by opening the contact between springs 709 and '711, due to the action offthe pins 7073, 7 072 and 707 actingupon the contact spring 709. TheA instant after the last pin 707 has swept past the spring 700, the pin 708 pushes the spring 710 out ot' contact with spring 712. The above result is obtained because of the fact that pins 707 and S move the springs 700 and 710 in a reverse direction in the return movement of the disk to that in which they are moved when the disk 7 00 is moved in the forward direction. Thus when the disk 700 is turning back to its normal position, the two line limbs 201 and 202 are keptfgrounded by the brush 70l and the grounding disk 7072, except duringthe interval when the pins 707, 702, etc., push the spring 709 out of contact with spring'711. Each timethis occurs, the earth connection is momentarily removed from line limb 201. The backward movement of the disk 700 likewise causes the'pin 708 to .move the spring 710 out of Contact with spring 712 and, consequently, the ground connection is momenta'rilyrre moved from the line llimb 202. The ground connection will be removed from both line Vof 'the number'o'f the subscriber wanted. The

interruptions of the line wire 201 cause vi.- brations of the armature 66 of the relay 221 at the fi-rst selector. The armature 66 sends impulses through the -lifting magnet 237 of the first selector, which then raises the arms 300, 301 and 302 to the desired level of bank contacts. After the contact arms 300, 301,I 302 have been raised to the desired level,.the wire 201is earthed at the calling station, while the yconnection 'through wire 202` is interrupted. This interruption 'in the wire 202 results in the' den'ergization of the line relay 225. v'The moment the selector vshaft carrying the brushes 300,301, 302 was raised out of its normal position, the contacts 68 and 69 forming a part of a'n offnormal switch were closed, so that on the momentary denergization of .the relay 225 a current impuls'elows from the negative pole of the battery throughl armature 70, contact 68, contact arm 69 of a synchronous circuit changer associated with the first se'-` lector .driving magnet 227 of the circuit changer to the positive pole of the battery.

iso

the test relay 223i of therst selector is then ldclosed immediately the line relay 225 is energized again from the negative pole of the batterythrough contact 79, 234, switch arm 7 3, wire 80, resistance 231, rotary olf-normal contact 81 to the positive pole of the battery.

vA current will also flow over wire 95 and through switcharm G9 through the driving magnet 227 of the. synchronous circuit changer. Shunt 231 will not allow sufficient current to flow through the driving magnet 227 to energize it. Theene-rgization of the relay 225i results in the energization of the rotary magnet 235 ofthe first selector by impulses flowing from the negative pole of the battery through armature contact 82, rotary magnet- 235,wire 83,-switcharm7l of circuit changer, interi-opter 236 to theI positive pole of the battery. After the rotary magnet has turned the 'brushes 300; 301, 302 one Step, the rotary olf-normal switch 81 is opened and the test relay 234: now receives current over the earthed test wires of busy, trunks, the test wires of busy trunks being earthed in a manner that will be presently described. IVhile the selector is testing for busy trunks, the test vrelay 23d and the driving magnet 227 will be in series in a circuit from the negative pole of the battery through 79, 234, 73, 80, 305, 69, 227 to the positive pole of thel battery. The windings of the relays 231 and 227 areso dimensioned as to prevent either of these magnetsbeing actuated or influenced when connected vin series with each other.

The test brush 302 is made so broad that it touches another fixed contact 303 before leaving the last. The moment the test brush 302 is set on to the fixed test contact 03 of an idle trunk. the current flowing from the test relay 234 is weakened so much as to cause' its armatures to retract, whereupon the ari'nature contact 82 opens the circuit of the rotaryvv magnet Immediately after the driving-magnet 227 of the synchronous circuit changer is energized by a current flowing from the negative pole of the battery through 85. S4. 69, 227 to the positive pole. This causes the driving magnet V227 to move the arms of the circuitlchanger into their third position III. The' moment this' third position is reached. the test brush 302 is earthed through the following circuit-4502. 232,-

switcharm 78. test wire 5S lthat leads to the distributing switch. test brush vQ52 of distributing switch. 57, 56,59. 60,-61, 62, earth.` 'lhc' resistance of the driving magnet 62 belonging tothe synchronous circuitchanger at the distributing switch is so low that the connection of the test wires- 58` and 30Jc through it to earth establishes the busy condition of the trunks leading from the distributing switch to the first selector, and

fromthe first selector to the final selector.

In case the calling subscriber replaces his receiver and abandons the call before the first selector has found an idle trunk leading to a filial selector, a special release circuit will come into action, this circuit consisting principally ofthe contacts 86, 87,'switcharm Tri, relay 306, and the vertical off-normal switch G9. -If the calling subscriber abandons the call before the first selector has reached an idle trunk, the denergization of the relays 212iv andf225 will result in the closure of the contacts 86 and 87, and the current will flow from the negative pole of the battery through 86, 87, 74, 88, 306, 69 to the positive pole.

It is to be noted that the moment a first selector is seized yby a distributing switch,

-its lifting magneti 237 receives an impulse causing the selector shaft to take an idle step, which resultsin the closure of the vertical off-normal switch 69.

The current flowing in the circuit described above through the relay 306 causes this relay to be energized, and to close a locking circuit for itself through its contact 89. It also closes a contact 90, and thus connects an interrupter 229 to the test wire 230. The interrupter now intermittently connects the negative pole to the test Wire,f and energizes the driving magnet 227 and 62 ofthe synchronous circuit changers at the first selector, and at the distributing switch. The synchronous circuit vchangers are designed to take one step the-moment their driving magnets are energized, and to take a second step the moment the energization of their driving magnets ceases. In the interval between two energizations of their driving magnets, the switcharms of the synchronous circuit changers travel over the short contacts indicated lbetween the long conta-cts I, II, III and so'forth. By providing contacts that are momentarily touched by the switcharms of the synchronous circuit changers in the intervals between the impulses that flow through the driving magnets, circuit' controlling functions may. be caused to take place during thc said intervals. The circuit controlling functions employed in this, system will be explained presently.

It has now. been explained how'l asub# scriber by prematuielyreplacing his receiver causes impulses toI rupter 229 through the driving magnets'l62 and 227 of the synchronous circuit changers belonging to the distributingswitch, and to the first selector. If the calling subscriber 112e, be sent from the interabandons the call ,at a moment when the firstv selector is hunting for a final selector .th

switch arms of the synchronous Ycircuit changer at the first selector will be in their position IIQ4 Thefabandoning of the call and the consequent closure of the contacts .86 and S7 will, therefore, result in the switcharms of the synchronous circuit changer .being moved by an impulse flowing through the interrupter 229 and through the contact 90, half the distance from positions I lII to the positions III. The' moment the l moment the driving magnet 62 of the circuit changer belonging to the distributing switch will also receive impulses through the interrupter 229 and the contact 90. Thusafter the switcharms of the synchronous circuit changer at the first selector'have reached the 1 position III, each new impulse sent by the interrupter 229V into the test wire 23()V will result in a simultaneous energization of the driving magnets 227and 62 of the synchrov nous circuit (':hangers at the first selector,

52a :tance between `two contacts-for instance and at the distributing switch, and each impulse ,will cause the switcharms ofboth circuit changers to progress half the dis- III and IV, and after each impulse ceases,

the switcharms will execute another half step so as to reach the succeeding Vlong conf tact.l The switcharms of the circuit changer at .the first selector will be caused to move forward step by step'in the manner 'described, until they reach the long contacts V,

and the switcharm 61 of the circuit. changer "atthe distributing switch will travel around in synchronism with the switcharms of the circu'it changerat the first selector until it reaches4 the long contact III.

The next .impulse sent by the interrupter ,22,9 over the Wire 230 will result in the Switcharm 74 travelin half the distance between the contacts and VI'and in the switcharm 6l travelin half the distance between the contacts I I and IV. The movment this last impulse from the interrupter 229 ceasesthe switcharms 74 and 73 and all` the .other arms of the circuit changer at the 'virst selector will execute a further step, and

in doing this the arm 7 4 brushes past acontact 228 and the arm 73 makes amomentary contact with the short contact 91. The arm 61 of the circuit changer'at the distributing lswitch'al-so executes a step from the point half'W-y between III and IV'synchronously with the arms 7 4 and 73 at the first selector.

The arm (Slfvbrushesv past the. contact 223 at the same `momen'tthat the'arms 74 and73 brush past the contacts 228 and'91. At the z moment when .the arms 73,' 74 and 61 touch their respective contacts 91, 228 'and 223, the

lreleasemagnets 233 and 217 of therrst selector andthe distributing switch 'are energized.- The current that energizes the release magnet o f the first selector flows from the. negative' pole of the batteryA through 86,

87, 74, 22S, 230, S0, 73, 91, 233 to the positive pole of the battery, and the current through the resetting relay 217 of the distributing switch, Fig. l, Hows from the negative pole o'f the battery through SG, S7, '71, 22S, 230,l 226, 78, 58, 252, 57, 5G, 59, 60, 61, 223, 217, to the positive pole. The release relayA closes a locking circuit for itself through its armature contact 93. By closing its armature contact 91, the releasev relay 217 connects the turning 1nagnet220 of the distributing switch to the interrupter 238, vso that vimpulses will now flow through the turning magnet 220 until the brushes 250, 251, l252 of the distributing switch reach their normal positions, in which the off-normal contact 50 is opened, and in which the other contacts of the off-normal switch are caused to assume their normal positions.

The'opening of the contact 50 causes the deenergization of the release relay 217, and all g parts of the distributing switchwill then haveregained their normal positions.v

It has now been described how the switches at the exchange are restored to their normal positions in case a subscriber y abandons the call before the group selector, Fig. 2, establishes a connection with an idle` trunk leading to a final selector.

IVe will now consider the ,case where the subscriberV abandoned the call when the group selector had made Connection with a' trunk leading to a inal selector. In this case, the moment the connection is extended to the lfinal selector, the relays 500 and 501 are energized. Contact 99 is immediately closed kand a circuit is formed which may be traced `from the negative pole of the battery through 99, arm 526 of side switch, lifting magnet 502 to the positivel pole of the bat` tery. T he 'selector shaft isthus'raised so as to take an idle step andfclose a contact 508 of a vertical of-normalswitch. The moment the calling subscriberl replaces his receiver in abandoning the ca.ll,-the contacts 600 and 601 of relays 500 and 501,'which were opened lbefore the olf-normal4 contact 508 was closed, will now establish a circuit' which may be traced from the negative pole of the battery through interrupter 521, contacts 601, 600, wire 124, switcharm l514 of synchronous circuit changer, driving ma net 509, o-normalcontact 508 to thepositive pole of the battery. The im ulses sent by the interrupter 521thr'ough the driving magnet 509 also flow back over wire 304 to the driving magnets of the'synchronous circuit changers at the group selector and-'the distributing switch, and thus the switcharms of all the synchronousv circuit changers-are .stepped forward in synchronism.

In taking their third step, after the impulses through `contacts 601 and 600r commencedfthe-release magnet at eachselectorA is energized and the switches .restored to iso.

Aim'

Acircuit.changer at the stepped into their position HI. Therefore their normal position. It Will be remem 4 bered -that when the connection was :extended to the inal selector at the group selector, the switclr arms of,v the synchronous roup selector were the third impulse vthat flows after the contacts 601 and600 are closed,- due to the. calling subscriber replacing" his receiver, will cause the switcharms of ,the synchronous cir'.- cuit ychanger atthe group selector to pass from position ,V t-4 .position VI. The switcharm 6'1 of, the synchronous circuit changer at the distributing switch 'F ig. 1 is in .its position III at the moment the impulses commence flowing through the con- .tae-ts 601 and v600.- Therefore'the third impulse that flows through the contacts`600 synchronous circuit changery at the final setravel from position V to position VI and the switcharm 61 at the distributing switch -to move from position III :to position IV. -In traveling from position III to IV the switcharmA 513 of the synchronous circuit changer ath-the final selectorl momentarily .connects the negative pole of the battery to the wire'304 that extends back to the group selector and distributing switch, thereforeat this moment an impulse will iiowl from the lnegative pole of the battery through the release magnets at cach switchthat is, through the magnet 510 at the iinal selector, 233 at the group selector and i throughthe release relay 217 at the distributing switch, Fig. 1. .The switches-will then all be restored to their normal positions.

,'It mustbe pointed out that the synchronous circuit changers are so arranged that when their switcharms have passed from'the first position to the last position shown on the'drawings, theya-re ready to recommence -a new -fc yele. of c1rcu1t changes corresponding iin character andsequence to those etl'ected in passing from positions I to VI, Fig. 2, or I to IVIFi-gs. 1 and 3.

. lVe will now consider 'the casel where a connection is made with an'ordinary line and the line 4desired is not bus v. The calling subscriber works'lns lmpulse transmitter, which earths the wire '202 and interrupts'the wire .201 in the manner' already deserlbed. and thus causes the rela)v 500 to l send the desired number of impulses through .97. 9S, side switch driving magnet 519', vertical; off-normal switch 50i', to earth. The

'scriber`s impulse transmitter.

Swiaimms 525, 526, 527,528, 52s', 515, 516,

518 take a step forward the moment the relaiT 5030i thc final selector' is connected to the impulse contact 99 of relay 500 through the switcharm 526. The calling subscriber now sends in the rotary impulses which cause the brushes 501, 505 and 506to be turned, and to be moved on to the contacts of the desired line, which we have assumed to be idle.V

The moment the changeover impulse is sent afterv the brushes have been movedon to the contacts ofthe wanted line, the armatures of relay 501 retract, and the circuit is4 closed from the negative pole of the batteryr through contact 100, 4test relay 520, ,contact arm 527 of side switch, to wire 107 and test brush 506. As the Adesired line yis idle, the

test brush 500will not-'be connected to earth through. the test contact leading to the desiredline, and therefore the test relay 520 will not be energized. Therefore contactv 108 will not be closed, and the impulse that is sent from the negative pole of the battery through 96, 9,7, l9S, 519, 50i' to earth will not be maintained at 108, but will stop iiowing the moment the relay 501 reattracts its varmatures so thatthe side switch magnet 519 will .illow the contact arms of the side switch to pass into their third position, and thus close the ringing circuit, which may be traced from the negatijge pole of the vbattery through contact 99, contact arm 526, inter rupter 5.15, ringing relay/ 524, to the positive pole of the battery. yThe interrupter 545 now causes the relay 52-1 to connect the line lcadingto the wanted subscriber to a source ot ringing current 54S at regular intervals. lVhen the wanted party. responds, his switchhook momentarily establishes a connection between either ofthe limbs of his line and ground, anti this causes the differential relaiv 52'.) to momentarily `attract its armature and close a contact 118, which causes an impulse to llow from the negative pole of the battery through 11S, 119, 9S, side switch magnet 519, contact 50T to earth. rl`he contact arms of the said switch are then caused to move into their fourth position. and the arm 520 in moving out of Vthe third position opens the ringing circuit. ConverF sation ma)v now tahe place. 'hen the wanted subscriber responds. a current also flows through a rela \Y 52?, which is energized and opens a contact 12;. The current which traverses the winding of relayfGlOl is insullicient to cause its encrgization as this rela)v \vill`onl v operate when the line wires at the subscribers station are short circuited. that when^the subscriber at the station equipped as `shown inl Fig. 6,'re-

. hereinafter.

. battery.

sponds. This Will be more fully explained If the-called subscriber is the first to replace his receiver .at the end of the conversation, a release circuit is closed at the contact 122, which may be traced from the negative pole of the battery through interrupter 521, Wires 111, 121, contact 122, wire 123, switcharm 515, switcharm 514, which is row in position II, driving magnet 509, contact`508 to the positive pole of the It must be mentioned that the driving magnet 509 received one impulse at the moment when the switcharms of the selector were moved out of their normal position by the first rotary impulse which caused the closure. of the rotary off-normal switch 511, and resulted in an impulse flowing from the negative pole of the battery through the interrupter 512, contact 511, switcharm 514 in its position I, driving magnet 509, vertical off-normal contact 50S to the positive pole of the battery. T his impulse caused the driving magnet 509 to send the switch- .arms and synchronous circuit changer from their positions I to II. IVe will now return .to the restoring operation that was initiated by the wanted subscriber replacing his receiver on lthe switchhook and' causing the relay 523 to be denergized. Itwasv seen' that to the `driving magnet 500. These impulses also commenced flowing back to the group selector and the distributing switch through wire 30i-and caused the synchronous circuit changers at the selectors to move synchronously with the, circuit changer at the final selector. The release magnets at-the final selector and at the distributing'switch are energized at the moment in which the synthrough the arm 513 from the negative pole of th'e' battery. and caused the restoration of all the switches to their normal positions.-

'hile the switcharms of the synchronous circuit changers were executing theirA synchronous movements in order to yetl'ect the circuit 4changer at the final selector passed tromposition II to III. At this moment the switcharm ot the synchronous circuit 'changer `at thc distributing switch' also passed from position II to III and the swltcharlns of the synchronous circuit charged.

impulses then commenced limiting,r 'through' the'interrupter 521 and contact` 122 it the contact arms of the side switch at the nal selector had not gone into lthe talking position. noy connection would have been established between the contact '125 and the wire 301 through the contact arm 516 of the side switch, and then no conversation is It` will now be assumed Vthat the desired station is a station that is connected to the calling line,-that is, that the calling subscriber is' lmalzing a revertive call. 'il he moment the rotary movement of the brushes 504, 505 and 506 commences, a lrotary o'lnormal switch 511' is closed, which connects an interrupterf512 to thea-driving' magnet 509 of a synchronous circuit changer allotted to thefinal selector. This circui'tchan er has two switcharms and514t.4 It will e noted that when the rotary: off-normal switch 511 is Iclo"s'ed.the interrupter 512, in addition to being connectedfto -the driving magnet '509 is also connected to the test wire 303i, which extends back to the' group selectorrand "to 4the distributing switch.

Thus the `moment the switch 5,11 isc'losed V an impulse will flow through the driving Vmagnets 509, 227 and '62` of-the ,synchronous circuit changers at the fn'al'selector, group selector and distributing switch. This results in the synchronous movements ofthe three circuit changers, and lwhile the .chronous circuit changer of thel final selec-f l tor executes the second half of lts. vtravel from the contact I to II, its-switcharm 513 momentarily connects the negative pole of the battery to thetest wire 304. lVhile the synchronous circuit changer at the 'final selector travels from position IV to II, the circuit changer at the group selector travels from position III to IV, and the -circuit changer at the distributing switch travels from its positionv I ,to II. 'Thus the switcharms 513. 78 and 61 will simultaneouslyT brush past contactsn530, 529 and respectively. The momentary connections at the three points just mentioned results in an impulse flowing-from the negative pole of the battery through 513 and 530. 304, 303, 302, 232. 7S. 58, 252,V 57, 5G, 59, G0, 61. 100, 101. relay 221. resistance 531, contact 52. to earth. The relay 221. vis energized. land closes a locking circuit for itself through its armature contact 102. By opening its con- 'l tact 103. the relay 221' removes the busyl condition of the calling line bv disconnecting the .earth frQmthe est wire' 256,.'but

`the-relay 221 also closes a contact 104, and .thus connects va relay 222 through 104 and 53 to.the wire 2 02 of the calling line.` The relay 222 is 'immediately energized, andby closing its. contact 105 immediately 1reconnects the'earth tothe test wire 256, and thus replaces the busy potential, which has been removed by the opening of the contact 103. The relayf222 vis the revertive connecting relay, its functionbeing to momentarily remove the -busycondition ofthe calling'line in the case of a reverted call, so as to enable revertive connections to be established. Its

operation will be more fully described presently.

It will be n'oted that the revertive connect-.i

ing relay 222 is connectedjto the one limb. of 1 the callingy line the moment the rotary im- .pulses for stepping the nal selector` on to the wanted line, which in this caseis also the I calling line, commence comingin. Af'ter all "the rotary impulses have been sent 1n, the.

changeover impulse will ensue, this ordinarily resulting in the wanted -line being tested as toits ldlefor busy condition. The test circuit at 'the final selector is established l by the chan over impulse causing the relay` 501 to .beenergi'zed, .and maybe traced from the negative lpoleof theA battery 1 through the armaturelcon'tact 106, test relay 520, side switcharm 52'?, wire 107, brush 506, test'wire 256, which isconnected in multi le'to the contacts in the contact banks of a the otherV final selectors 4in the same group. In the case of a revertive call, however the calling-line .momentarily removes the busy condition from its test wire by means of the revlertiveconnecting relay `222 by opening its cntact 105. From the moment in which the rotary impulses commence revertive connection relay 222.

turning the brushes of the final vselector to 'the contacts of 'the wanted line-that is,

from the moment. the driving magnet 5094 of the synchronous circuit changer at the final selector receives an impulse from the interru ter 512, due t0 the closure of the rotary o -normal switch 511, which causes the switcharms 514l and 513 of thefsynchr'onous circuit changer to travel from their position I to II-relay 222 at the distributing switch is energized. The excitation of the relay 222 'iscaused in the manuel' described above bythe switcharm 513 sending an impulse` through contact 530 of the final selector to the distributing switch. After the had been connected vto the one limb of thezca'lling line, further rotary impulses* Would generally flow through the relay 500. VDuring the `flowing' of these. impulses, the limb 202 of the calling line vwill be kept earthed, so that the, relay 222 is kept constantly energized.' Af-i ter the rotary lmpulses have all been sent in" and the .switcharms 504, 1505 506 have:

Yreaeheid the contacts of the Wanted line, which 1n this case is also the acalling line, a

changeover impulse will ensue, this being caused by earthing the' Wire '201, and at 4the same time opening the limb 202. This causes the simultaneous denergization of the relay' 501 and the reyertive connecting relay The revel-tive connecting relay opens its con- .l tact 105 and. momentarily removes the busy test, so that no current will How through the busy test circuit which, as will be remembered, is ,to be traced from the negative pole of thebattery through 106, 520,- 527,107, 506,256, 105, 52, to earth. Asv the .side

4switch magnet 519 is not kept energized by the contact'lOS of the' test relay atgthe filial selector, the switcharms 525, 526, etcr ofthe side switch move into -theirfthird` position. In this position of the switch'arms, the ringing relay. 524 at the iinal selector is inter- -mittently energized by 'a current fiowing" lsusV drawings alsingle ringing current source is AAshown at' 548. lFrom this point on the op-l eration is the saine as that described in con-A nection withan ordinary call.

At the moment when the brushes 504, 505 i and 506 of the-,final selector reach the contacts of the wanted line, a relay 523 will be .l

energized if the call is .a revertiveone'. If the call is not reyertive, the relay 523 is only energized when the Wanted station responds;-

In' any case the relay 523 is energized before the side switcharm's 515 and 516`move into their fourth position. By opening the contact 122 'and thus opening .the circuit from theinterrupter 521 through 111, 121 to 123 before the called party answers, current im-l pulses are prevented from flowing from the interrupter 521 through the driving magnet 509 and through the driving magnets of the other synchronous circuit changers, and thus causing .prematurely the release which should .take .place later when v,the called sub'- scriber' replaces' hisreceiver Aafter having responded to the c'all. .The-restoration of the apparatustakes placein precisely theAv .same manner asl in the case of an ordinary call, and will not therefore beidescribed. f1 I ,As previously indicated, relay. 610 will n"hen the calledline is lthestatien .showngin .ing his receiver, thez resulting' upward move-1 12B operate only when thefline loopis short cirf icu'lted at the subscribers stationfi 'Ihusll t. oi"- the ,switch hook momentarily vshort circiiiting of the line does not affeetthe`ditierentially Wound relay 522, but

"operates relays\610. and 523.- The operation of 'relay'610- closes a circuit from battery 'through 611,119, 98 andv 519 to ground. 'This in o'ves'the side switch arms from the ringing to the talking position in a' manner identical to that 'described in connection with the operation of the differential relay 522, which operates whenever any one of the other three subscribers on the line responds.

' Relay 610 is so designed that it can be adof relay 610, F ig. 3, considerable diliiculty would be experienced in adjusting the relay so 'that it would release its armature after the saine had been 'pulled up because' this relay is not completelyA denergized after the line loop has been short circuited by the' springs 600 and 601, but is kept y energized by a relatively weak current which subsequently flows through Contact 607, transmitter 608 and the induction coil 609. To insure a proper release ofthe armature of relay 610, this relayniay be specially constructed as shown in Fig. 10. As illustrated, the relay has in addition to the contact 611, which is used to close the circuit of relay 519, Fig. 3, another contact 612 and a .link 613 which turns on a Jivot 611 and is hinged at 615. lVhen the relayis energized, the armature 612 sweeps against the lower Vend of the oblique surface 616 fand pushes the link 613 aside. As soon as the armatures 61.1 and 612 areA fully attracted, 612 makesv contact with 618 and thereby short circuits the winding of relay 610 through a connection 619. The armature of the relay, therefore, is pulled back bythe spring 620 but'tlie short circuit through the contact 612 and lead 619 is not removed untilthe link 613 has been raised a considerable distance by the armature '612. As soon as the arma- 5 tures have returned to practically normal position, the ,upper end of the oblique surface 616 engages with a pin 621 and the link 613 is then pushed aside suiiiciently to liberate the armature 612 from the catch 022. As the armatures have now retracted a considerable distance from the magnetic pole of the relay, there is no danger of the armatures being reattracted by the relatively -weak current which now flows through the the ,busy condition at the niomenta revertive line 'loop as indicatedl in F ig. 6.l

If an ordinary relayl connected from the line as soon as it has ac- 70 complished its purpose.A This can be done by providing an additional position on each of the synchronous circuit changers at the 'distributin switch group selectors and final selector. yhis additional position would be 76 arrangedgbetween the positions I and III of each'sylichronous switch. The circuits at t," flnal selectorwould then be so arranged "'at at the moment when `the switcharms 525, 526, etc. of the side switch move from I0 their second into their third position,-that 1s, into the ringing position-the driving magnet 509 ofthe synchronous circuit changer receives an impulse which causes the switcliarms 514 and 513 tov move from I6 their position Il to the additional position. This impulse wouldalso cause the synchronous circuit changer at the group selector to `move-from its position IVjto'the additional position, and would result in moving the 910 switcliarni 61 at the -distributing switch from position Il to the additional position. In executing the second half of this additional step, the switcharm 513 at the final selector momentarily connects the 'negative )5 pole of the battery to the wires 301, 232 and 5S, and thisconnection to the negative po 1e of the battery would be extended over 57, 56, 59, 60, 61 tothe wire 120, which is connected to a Contact located at the additional 1.00

position of the circuit` changer at the distributing switch. tion of the wire 120 to the negativeA pole ofv the battery-would cause the relay 221'1to be shortcircuited so that it would open its armature 'cont-act 104, and thus would dis-v connect relav222 from the line limb 'hat I claim is 1. ln a telephone exchange system, the

combination with a plurality of lines. automatic selectin' switches adapted to intercon ncct the saine. meters for said lines, electromagnetic means associated with each of said switches adapted to release the saine, a

circuit adaptedE to actuate the meter of the 115 callingflinc. a circuit adapted to` actuate said electromagnctic release means, said circuits heingclosed over the same conductor which is associated with said meter and said electromagnetic release means at diifer- 12 cnt times to actuate the Sallie, and synchronous switches adapted to associate the saine therewith at the proper times.

2. ln a telephone exchange system, the

combination with a plurality of party lines,'1,

automatic selector switches adapted to inter-r connect the saine including group and final selector switches. meters for said lines, electromagnetic means associated with each selector adaptcd to release the same, electrol This momentary connec- 4 magnetic means for establishing a busy condition on the multiple terminals of the calling line in said final selector switches upon the initia/tion of a call, electromagnetic means for removing said busy condition. a circuit adapted to actuate the meter of the calling line, a circuit adapted to actuate said `electromagnetic reiease means. a circuit selector adapted to release the same, electrol magnetic means for establishing a busy condition on the 4multiple terminals of the calling line in said final selector switches upon tl e initiation of a call, electromagnetic means for removing said busy condition, a circuit adapted to actuate the meter of the calling line, a circuit adapted to actuate said electromagnetic release means, a circuit adapted to actuate said electromagnetic busy-condition removing means at the 1noment of test by said linal selector. said circuits comprising the same conductor which is associated with said different electromagnetic means at diii'erent times to actuate the same. and synchronous switches adapted to associate the same therewith at the proper times.

combination with a plurality of lines, automatic selector and distributing switches adapted tov interconnect the same, a meter for each party on a line, a circuit`for .operating said meters, electromagnetic means actuated upon the initiation of a call by one ot' the parties of a party line for preparing` the corresponding meter for operation and for causing the operation of one of said distributing switches to seek a first selector and means for thereafter closing said meter circuit to actuate the selected meter.

(i. In a telephone exchange system, the combination with a plurality-of party lines,- a meter for each party of a line, a circuit` for operating the meters, electromagnetic means actuated upon the initiation of a call by any of the parties on a line for preparing the corresponding meter Jfor operatiomone of said parties causing the corresponding meter to be prepared by the simple closure of the line loop, and electromagnetic means actuated by any of the other parties in initiating a call and before the closure of the line loop to prevent the meter of the party Vprepared by the closure of the line loop from being so prepared.

T. In a ltelephone exchange system, the combination with a plurality of four-party metallic telephone lines, a meter for each party of a line, a circuit for operating the meters. electromagnetic means adapted to be actuated in four different ways by four ditt'erent electrical conditions caused by the initiation of calls by said parties for preparing=the corresponding meter for opera-A tion. one of these being the simple closure of the line loop. and electromagnetic means actuated by the creation of each of the other three conditions to prevent the preparing of the meter circuit of the line whose meter circuit is closed by the closure of the line loop upon the subsequent closure of such loop by any of the other parties.

In witness whereof. I hereunto subscribe my name this 30th day of April A. D., 1913.

FRITZ ALDEDORFF.

lVitnesses: I 1

PAUL Kousen HARRY T non SHERMAN. 

